Hi everyone long time looker first time poster, I have a 98xj 4.0 Auto, its got 283k on it with only minor issues like freeze plug leaking into bell housing . Now I have the p1391 code, put in new Mopar crank sensor still have code, put in new Mopar cam/ pick up sensor coil, still has code. Checked wiring to o2 sensor ect. and all grounds. Put #1 at TDC with harmonic balancer on TDC and pin fits like a glove into slot in distributor with no play in shaft. What am I missing? SES light comes on as soon as i start it twice, but runs fine. I can unplug crank sensor with jeep running and it kills the engine, unplug cam sensor engine stays running.

Hi everyone long time looker first time poster, I have a 98xj 4.0 Auto, its got 283k on it with only minor issues like freeze plug leaking into bell housing . Now I have the p1391 code, put in new Mopar crank sensor still have code, put in new Mopar cam/ pick up sensor coil, still has code. Checked wiring to o2 sensor ect. and all grounds. Put #1 at TDC with harmonic balancer on TDC and pin fits like a glove into slot in distributor with no play in shaft. What am I missing? SES light comes on as soon as i start it twice, but runs fine. I can unplug crank sensor with jeep running and it kills the engine, unplug cam sensor engine stays running.

Do a reset on the ecu. I hook the battery + cable and ground it out ( can be on the ac compressor ) for 30 seconds. Put it back on. Turn the key to on but donít start. Turn the headlights on for 10 seconds, then off. Now start. It will relearn over the next 50 warmups.

Often replacing the sensor fixes this code, but not necessarily. Therefore it's important to check the following:

•Check that the wiring isn't routed too close to sharp metal edges, or to hot exhaust parts.
• Visually inspect the wiring at the sensor for any burn marks, discoloration indicative of melting or chafing of insulation
• Visually inspect the cam sensor for damage
• Visually inspect the reluctor wheel inside the alternator. Make sure the magnet is firmly attached.
• If all checks out okay, then replace the sensor.

If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.

A mis-indexed distributor/cam sensor may exhibit surging, light bucking or intermittent engine misfiring. This will most likely occur when the vehicle is at operating temperature and under a light load at approximately 2,000 rpm. The proper indexing procedure must be used as outlined in the Jeep Service Manual.

Reset the ecu, code came back 2nd time I started the engine. What should I try next? The distributor doesn't have any side to side play only some play when I try to turn the rotor back and forth and I can't find any info about how much play in allowable, should I replace to distributor??

I tried to check for timing chain slack, I put #1 at TDC and the harmonic balancer there also, then slowly turned the crank the opposite direction til the rotor turned. Looks like I had to move the crank to the 5 degree mark until the rotor began the turn. I that to much play?? Can't find a spec on it.